Firefly, also lightning bug, common name for any of a large family of luminescent beetles. There are about 1100 species found throughout tropical and temperate regions. Adult fireflies are elongate, relatively soft-bodied beetles up to 2.5 cm (up to 1 in) long. The common North American species are about 1 cm (about 0.4 in) long. They are dark colored but may have yellow or orange markings. Luminescent glands are located on the undersides of the rear abdominal segments (see Bioluminescence). Both sexes usually fly, and they emit intermittent light signals to attract mates or prey. They are often seen in meadows on late spring and summer nights. The larvae of fireflies are active, ground-dwelling predators. The larvae of some species are also luminescent and are called glowworms, a term also applied to phengodid beetles, a closely related family.

Fireflies are the sole bearer of the Flash ability, and they have the durability to see that it gets delivered to the enemy. With an incredible defense granted by their beetle-like carapaces, they can enter a fray and blind all units there, friend and foe alike, reducing combat to a pure melee. Which, if your army is built accordingly, can be a spectacular advantage.